Disk drive with identical top and bottom heads having three side-by-side elements and a common terminal pad

ABSTRACT

A magnetic recording disk drive uses side-by-side read/write heads formed on head carriers that are identical for both top and bottom disk surfaces. Thus, a common head carrier functions as a single manufacturable part usable for both top and bottom disk surfaces. The common head carrier has a trailing end with a pattern of components formed on it that includes three side-by-side transducers (two read elements equally spaced about a center write element) and five terminal pads, one of which is a common pad, and all of the electrical connectors interconnecting the five terminal pads with the three transducers. There are only three terminal pads for the two read elements, with one of the read terminal pads being a common terminal pad that is electrically connected to both read elements. During assembly of the disk drive, the common carrier, when used as the top carrier, has a first read terminal pad and the common terminal pad connected to the leads on the suspension. When used as the bottom carrier, the second read terminal pad and the common terminal pad are connected to the leads on the suspension. Thus, only one carrier common to both top and bottom sides of the disk needs to be manufactured. The uniqueness of the top and bottom carriers is obtained by the wiring connection of the read terminal pads to the leads on the suspensions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/811,490filed Mar. 5, 1997, now U.S. Pat. No. 5,798,890.

TECHNICAL FIELD

The invention relates in general to magnetic recording disk drives, andmore particularly to magnetic recording disk drives that useside-by-side read/write heads.

BACKGROUND OF THE INVENTION

Disk drives, also called disk files, are information storage devicesthat use a rotatable disk with concentric data tracks containing theinformation, a head for reading and/or writing data onto the varioustracks, and an actuator connected to a carrier for the head for movingthe head to the desired track and maintaining it over the trackcenterline during read or write operations. There are typically aplurality of disks separated by spacer rings and stacked on a hub thatis rotated by a disk drive motor. A housing supports the drive motor andhead actuator, and surrounds the head and disk to provide asubstantially sealed environment for the head-disk interface.

In conventional magnetic recording disk drives, the head carrier is anair-bearing slider that rides on a bearing of air above the disk surfacewhen the disk is rotating at its operational speed. The slider ismaintained next to the disk surface by a suspension that connects theslider to the actuator. The slider flies over the disk surface as aconsequence of a balance of the spring force from the suspension and theair pressure generated by the velocity of the rotating disk. In avariation of the conventional air bearing, a combined air and liquidbearing supports the slider, which is in very close proximity or actualcontact with a relatively thin lubricant film on the disk. Disk drivesof this type are described in U.S. Pat. No. 4,901,185 assigned toToshiba and U.S. Pat. No. 5,202,803 assigned to IBM.

The most common form of disk drive actuator is a rotary actuator thatmoves the head carriers in a nonlinear, generally arcuate path acrossthe disk surfaces. Typically, there are two head carriers per disk, onefor each of the "top" and "bottom" disk surfaces, that are attached tothe actuator so that the carriers move in unison on the oppositesurfaces of the disk. The conventional arrangement for reading andwriting data is the well-known "cylinder mode". In this arrangement,continuous data is written by the top head writing to the top disksurface, followed immediately by the bottom head writing to thecorresponding track in the same "cylinder" on the bottom disk surface.Cylinder mode operation allows reading and writing on a data track onone data surface, to be immediately followed by reading or writing onthe corresponding data tracks (i.e., the data tracks in the samecylinder) on other data surfaces with little or no repositioning of theactuator. In disk drives that use noncylinder mode, there is norequirement that the heads on different disk surfaces be generallyaligned with one another because data is typically written by writingfirst to one disk surface on adjacent tracks and then followed bywriting to other disk surfaces on adjacent tracks.

Because the rotary actuator moves in an arcuate path, the sensing endsof the heads are not always aligned perpendicular to the data tracks,but are skewed relative to the tracks, the amount of skew varying withradial position. Recent disk drives use dual-element heads, i.e., aninductive coil element for writing and a magnetoresistive (MR) elementfor reading. One problem that arises with dual-element heads in rotaryactuator disk drives with inherent skew is that because the two elementsare spaced from one another in a direction perpendicular to the trailingend of the carrier, a rotary actuator is not able to maintain bothelements in simultaneous alignment with the data tracks due to theinherent nonlinear path across the disk surface. To compensate for this,dual-element heads are typically fabricated with the read and writeelements slightly offset from one another in a direction parallel to thetrailing end of the carrier, the amount of offset being determined bythe average skew of the heads. However, this solution is only optimal atone specific angular position of the rotary actuator and becomesunacceptable at high track densities where the data tracks are veryclosely spaced. An additional problem with dual-element heads in bothrotary actuator disk drives and linear actuator disk drives is thatbecause the elements are closely spaced on top of one another on thetrailing end of the slider so that both elements can be aligned with thesame data track, the magnetic field from the inductive write element canalter the magnetization state of the nearby MR read element.

Side-by-side, dual-element heads have been proposed to address theseproblems. In a side-by-side head, the write gap (i.e., the sensing end)of the inductive coil write element and the MR sensing film of the MRread element are located in the same plane on the trailing end of theslider but are spaced apart from one another in a direction parallel tothe slider trailing end. In this design, the read and write elements arenot simultaneously located over the same track so it is necessary forthe actuator to move the slider if read and write operations are to takeplace sequentially on the same track. Side-by-side, dual-element headsare described in U.S. Pat. Nos. 5,229,901 assigned to DEC and 4,729,048assigned to Sony. In these designs, a single write element and a singleread element are located on the trailing end of the slider. However,since the read and write elements on the top data surface of the diskmust be aligned with their counterparts on the bottom data surface ofthe disk if the disk drive is to operate in cylinder mode, theside-by-side head associated with the top surface of the disk must bethe mirror image of the side-by-side head associated with the bottomsurface of the disk. The result is that two different types of headsmust be fabricated: one for the top surfaces of the disks and the otherfor the bottom surfaces of the disks. This complicates the headmanufacturing process and disk drive assembly process.

An additional problem with both conventional dual-element heads andside-by-side, dual-element heads is that if either the read element orwrite element is determined to be bad after manufacturing, the entirehead carrier is rejected.

What is needed is a slider with a side-by-side read/write head structurethat can be manufactured at a higher yield and can function as a singlecommon part for use on both top and bottom data surfaces, therebyresulting in a disk drive with identical side-by-side heads on all disksurfaces.

SUMMARY OF THE INVENTION

The invention is a magnetic recording disk drive that uses a common headcarrier for both top and bottom disk surfaces. The common head carrierhas a trailing end or surface with a pattern of components formed on itthat includes three side-by-side transducers and sets of terminal pads.In the read/write/read side-by-side head arrangement, the first elementis a center write element, such as an inductive coil, and the second andthird elements are read elements, such as magnetoresistive readelements, that are generally equally spaced from the center writeelement. During the last stages of the fabrication process of the commonhead carrier, a lithographic mask is used to electrically connect one ofthe read elements with a selected set of terminal pads to personalizethe carrier as either a top or bottom carrier. Alternatively, each readelement is electrically connected to its own set of terminal pads duringfabrication of the common head carrier, thereby eliminating the need forany personalization of the carrier, with the appropriate set of padslater being electrically connected to the wiring on the suspension attime of assembly. As a result, the disk drive can operate in cylindermode with side-by-side heads using a common carrier for both top andbottom disk surfaces.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be made to the following detaileddescription taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a block diagram of a prior art rotary actuator magneticrecording disk drive of the type capable of incorporating the presentinvention.

FIG. 2 is a sectional view of a prior art dual-element read/writemagnetic recording head.

FIG. 3 is an illustration of the present invention of top and bottomhead carriers with a common pattern of components, and each with athree-element read/write/read head, depicted in air-bearing relationshipwith respective top and bottom data surfaces of a magnetic recordingdisk.

FIG. 4A is an illustration of the trailing end of the common carrier ofthe present invention with the common pattern of components comprisingthe three transducers and four terminal pads.

FIG. 4B is a representation of the lithographic mask used to pattern theunique electrical conductor patterns onto the trailing end of the commoncarrier of FIG. 4A to form a top head carrier.

FIG. 5A is identical to FIG. 4A and is an illustration of the trailingend of the common carrier of the present invention with the commonpattern of components comprising the three transducers and four terminalpads.

FIG. 5B is a representation of the lithographic mask used to pattern theunique electrical conductor patterns onto the trailing end of the commoncarrier of FIG. 5A to form a bottom head carrier.

FIG. 6 is a second embodiment of the present invention illustrating acommon head carrier with a three-element read/write/read head and sixterminal pads that can be used for both top and bottom carriers byuniquely connecting appropriate terminal pads to wiring on the top andbottom suspensions.

FIG. 7 is a third embodiment of the present invention illustrating acommon head carrier with a three-element read/write/read head and fiveterminal pads, one of which is a common read element pad, that can beused for both top and bottom carriers by uniquely connecting appropriateterminal pads to wiring on the top and bottom suspensions.

DETAILED DESCRIPTION OF THE INVENTION

Prior Art

A conventional prior art disk drive of the type capable of incorporatingthe present invention is shown schematically in FIG. 1.

A magnetic recording disk 10, having "top" 11 and "bottom" 12 datasurfaces, is supported on a spindle 6 and rotated by a disk drive motor8. The magnetic recording media on each disk surface 11, 12 is in theform of an annular pattern of concentric data tracks (not shown).

A "top" head carrier 13 is positioned on the top surface 11 of disk 10.Carrier 13 is an air-bearing slider having an air-bearing surface ordisk side 20 and a trailing end 22. The head carrier 13 supports a priorart dual-element read/write head 21 on its trailing end 22 for readingand writing data to the magnetic media on disk surface 11. The carrier13 may be a three-rail, air-bearing slider of the type described inIBM's U.S. Pat. No. 4,894,740, with the head 21 being located on thetrailing end of the center rail. Carrier 13 is attached to an actuatorarm 14 by means of a suspension 15. The suspension 15 provides a slightspring force that biases the carrier 13 against the disk surface 11. A"bottom" carrier 17, also supporting a dual-element read/write head, ispositioned on the bottom surface 12 of disk 10 and is attached to anactuator arm 18 by means of a suspension 19.

Actuator arms 14, 18 are attached to a rotary actuator 27. The actuator27 is typically a voice coil motor (VCM) that comprises a coil movablewithin a fixed magnetic field, the direction and velocity of the coilmovements being controlled by the motor current signals supplied by acontrol unit 29. As the disk 10 rotates, the rotary actuator 27 movesthe carriers 13, 17 in a generally arcuate path radially in and out overtheir respective disk surfaces 11, 12 so that the read/write heads mayaccess different portions of the disk surfaces where data is desired tobe read or recorded.

In the conventional type of air-bearing disk drive, the rotation of thedisk generates an air bearing between the carrier and its associateddisk surface. The air bearing thus counterbalances the slight springforce of the suspension and supports the carrier off and slightly awayfrom the disk surface by a small, substantially constant spacing duringoperation. However, the present invention to be described below is alsoapplicable to other types of disk drives, such as contact ornear-contact recording disk drives, wherein the head carrier is urgedinto contact with the disk during read and write operations.

The various components of the disk storage system are controlled inoperation by control signals generated by control unit 29, such asaccess control signals and internal clock signals. Typically, thecontrol unit 29 comprises logic control circuits, storage means, and amicroprocessor, for example. The control unit 29 generates controlsignals to control various system operations, such as drive motorcontrol signals on line 23 and track position and seek control signalson line 28. The control signals on line 28 provide the desired currentprofiles to optimally move and position the carriers 13, 17 to thedesired data track on the respective disk surfaces 11, 12. Read andwrite signals are communicated to and from the read/write heads, such ashead 21, by means of the read/write channel 25. Because the read/writehead 21 is a dual-element head that includes an MR sensor for readingdata, a current source (not shown) is used to apply a sense current tothe MR sensor, and the read/write channel 25 includes MR signalamplification and detection circuitry. The suspensions 15, 19 haveelectrical wires or patterned conductors formed on them to provideelectrical connection between the read/write channel 25 and theread/write heads on carriers 13, 17.

The above description of a typical prior art magnetic recording diskdrive and the accompanying illustration of FIG. 1 is meant to berepresentative of many types of disk drives. For example, disk drivesmay contain a number of disks and rotary actuators, and each actuatormay support a number of head carriers. Also, while a rotary actuatordisk drive has been described, the present invention as described belowis also applicable to disk drives that use linear actuators.

Referring now to FIG. 2, the prior art dual-element read/write head 21formed on carrier 13 is shown in sectional view to illustrate the filmsmaking up the structure. The basic head comprises separate read andwrite structures formed over each other and sharing some commonelements. The write transducer is a thin film inductive elementcomprising coil 46 and pole pieces 40, 42 that define a sensing end orwrite gap 44 on the disk side 20 of the carrier 13. The copper coil 46is shown in sectional view between the pole pieces 40, 42. A first MRshield 50 is deposited on an oxide film grown on the trailing end 22 ofcarrier 13. The inductive pole piece 42 also serves as a second MRshield. MR shields 42, 50 are spaced apart from the MR sensor film 52,which is located in the middle of gap material 56 between the twoshields. The MR sensor film 52 has a sensing end 58 on the disk side 20of carrier 13. The MR sensor film 52 has electrical leads attached toits ends, such as lead 60 shown in FIG. 2. Since FIG. 2 is a sectionalview showing the interior of the read/write head 21, the opposite halfof MR sensor film 52 and its associated electrical lead are not shown.The electrical leads are connected to the current source to supply asense current through MR sensor film 52 that is used to detect changesin resistance corresponding to changes in magnetic flux from themagnetic recording disk. The MR sensor film 52 and the coils 46 of thewrite transducer are electrically connected to the circuitry making upthe read/write channel 25 (FIG. 1). As shown in FIG. 2, the sensing endsof the write and read transducers, i.e., write gap 44 and MR sensing end58, intersect in the same plane 57 that is generally perpendicular toboth trailing end 22 and disk side 20 of carrier 13. The sensing ends ofthe write and read transducers on the bottom carrier 17 (FIG. 1) alsointersect in this same plane. This is the conventional arrangement ofthe carriers to enable the read and write transducers to operate in thewell-known "cylinder mode". Cylinder mode operation allows reading andwriting on a data track on data surface 11 to be immediately followed byreading or writing on the corresponding data track (i.e., the data trackin the same cylinder) on data surface 12 with little or no repositioningof the actuator.

One of the problems with the prior art dual-element head shown in FIG. 2is that the head must be fabricated so that the center line of thesensing ends of the read and write transducers are slightly offsetlaterally from one another in a direction parallel to the length of thesensing ends that face the disk. This is because the sensing ends arelocated on top of one another (e.g., gap 44 on top of MR sensing end 58)instead of being in the same plane. The lateral offset is selected tocompensate for the skew of the rotary actuator and thus allows the readand write sensing ends to be precisely located over the same track,typically in the middle of the band of tracks. However, because thebottom carrier on the bottom data surface of the disk must be the mirrorimage of the top carrier on the top data surface, two separate carriersmust be fabricated. This means that two different carriers, withdifferent part numbers, must be manufactured and then tracked throughthe disk drive assembly process to assure their assembly on the propersuspension and actuator arm.

Preferred Embodiment

Referring to FIG. 3, there is depicted a magnetic recording disk 100having a top data surface 102 and a bottom data surface 104, and top andbottom head carriers 110, 112, respectively, on their air-bearingrelationship with respective data surfaces 102, 104. The disk 100 andtop and bottom carriers 110, 112 correspond to the disk 10 and top andbottom carriers 13, 17 depicted in the disk drive system of FIG. 1. Thedata surface 102 of disk 100 is shown with a plurality ofschematically-represented data tracks, such as typical data track 103shown in an end view. Each of the data tracks on top surface 102 has acorresponding data track on the bottom surface 104, such as data track105 corresponding to data track 103. The data tracks 103 and 105 arealigned in substantially the same "cylinder" centered about the centerof disk 110 to enable reading and writing of data consecutively on datatracks 103 and 105 in the conventional cylinder mode.

The top head carrier 110 has a trailing surface or end 120. Trailing end120 of top carrier 110 has a disk side edge 122 that faces disk 100 andis located near the disk side or air-bearing surface side of the disk110, and a back edge 124 is located near the back side. The trailing end120 of top carrier 110 has a pattern of components formed on it thatinclude a first element or transducer 130, a second element ortransducer 132, and a third element or transducer 134. In the preferredembodiment shown in FIG. 3, the first transducer is a conventionalinductive coil write element having a coil 137 and sensing end 131 inthe form of a gap that faces the data surface 102 of disk 100. Thesecond and third transducers 132, 134 are generally equally spaced fromthe center of write transducer 130 and comprise conventionalmagnetoresistive (MR) read elements. The second transducer 132 is an MRread element having a sensing end 133 that faces the data surface 102,and the third transducer is an MR read element having a sensing end 135that faces data surface 102. The pattern of components on trailing end120 also includes a plurality of terminal pads 140-143 and electricalconductors 152, 153 that interconnect two of the terminal pads 142, 143with the coil 137 of write transducer 130. The two terminal pads 142,143 thus form a first set of the total plurality of pads 140-143, andthe remaining terminal pads 140, 141 form a second set of the pluralityof terminal pads. The write transducer 130, the read transducers 132,134, the terminal pads 140-143, and the electrical conductors 152, 153together form a pattern of components on the trailing end 120 of carrier110, and are formed in the conventional well-known manner forfabricating inductive thin film write elements and magnetoresistive readelements. The methods of depositing the specific films to form the readand the write elements and pads are not part of the present invention.

As thus described, the top carrier 110 supports a three-elementread/write/read head wherein the three elements are formed in aside-by-side relationship with the two read elements 132, 134 spaced asubstantial distance from write element 130 so that the carrier 110 hasto be repositioned if data is to be read from a data track immediatelyafter the data has been written to that data track. This spacingdistance is approximately in the range of 10 to 100 microns. It shouldbe apparent that this structure is thus different from the conventionaldual-element head where the read and write elements are formed on top ofone another so that they are aligned with the same data track,essentially as shown in FIG. 2.

Referring now to bottom carrier 112, the carrier 112 has a trailing end160 with a pattern of components identical to the previously-describedpattern of components of the trailing end 120 of top carrier 110. Theonly difference between the trailing end 120 and trailing end 160 is inthe electrical conductors connecting the specific MR read element, i.e.,either second transducer 132 or third transducer 134. In the top carrier110, electrical conductors 154, 155 interconnect terminal pads 140, 141,respectively, with the second transducer 132. However, in the bottomcarrier 112, different electrical conductors 156, 157 interconnectterminal pads 140, 141, respectively, with the third transducer 134.

As shown in FIG. 3, the top and bottom carriers 110, 112 are attached tothe actuator (not shown) such that the center lines of the sensing ends131 of the first transducers 130 on both the top and bottom carriers arealigned in the same plane that is perpendicular to both the trailingends 120, 160 and the data surfaces 102, 104. This alignment allows thedata to be written in cylinder mode when the sensing ends 131 of thefirst transducers 130 are aligned with a data track. Similarly, becausethe two read transducers are equally spaced from the center of thesensing end 131 of the write transducer 130, the second transducer 132on top carrier 110 is aligned with the third transducer 134 on bottomcarrier 112. Thus, in the preferred embodiment of the present invention,the need for two separate carriers for the top and bottom carriers iseliminated by the use of the three-element read/write/read design,wherein the top and bottom carriers 110, 112 have the identical patternof components. The top and bottom carriers 110, 112 are personalized bythe electrical conductors that wire the appropriate read elements of thethree-element set to pads 140, 141. These electrical conductors areformed as the last step in the fabrication process.

Referring to FIGS. 4A-4B, there is depicted first in FIG. 4A the commoncarrier having a pattern of components that includes the central writeelement 130, the second and third read elements 132, 134, and the fourterminal pads 140-143. FIG. 4B is a representation of the personalizedlithographic mask used to pattern electrical conductors 152, 153 and154, 155 onto the common pattern of the trailing end of the carrierdepicted in FIG. 4A. When these electrical conductors are patterned, asessentially the last step in the fabrication process of the carriertrailing end, the result is the top carrier 110 with trailing end 120 inwhich the second read element 132 is electrically connected to pads 140,141 (FIG. 3).

FIG. 5A represents the identical carrier having the identical pattern ofcomponents as that shown in FIG. 4A, and FIG. 5B represents thepersonalized lithographic mask used to pattern electrical conductors152, 153 and 156, 157 onto the carrier of FIG. 5A. When these electricalconductors are so formed as part of the final personalization process inthe fabrication of the carrier, the carrier becomes the bottom carrier112 with the trailing end 160 in which the third read element 134 iselectrically connected to pads 140, 141 (FIG. 3).

The personalization masks depicted in FIGS. 4B and 5B could include justthe electrical conductors for the respective second and thirdtransducers since the electrical conductors 152, 153 for the firsttransducer are identical in both cases. In that case, the electricalconductors 152, 153 would form part of the identical pattern ofcomponents on both the top and bottom carriers.

Referring now to FIG. 6, there is illustrated a second embodiment of thepresent invention wherein a trailing end 200 of a common carrierincludes six electrical terminal pads 170-175, with each of the threetransducers being wired to two separate pads. In this embodiment, thetrailing end 200 of the carrier has an identical pattern of componentsfor both the top and bottom carriers. That pattern includes the threetransducers, the six pads, and all of the electrical connectors. Thisprovides the advantage that the entire fabrication process is identicalfor both top and bottom carriers, and the finished carrier can be usedfor both top and bottom carriers so that there is no need for apersonalization process. During assembly of the top and bottom carriersinto the disk drive, only the desired read element is electricallyconnected to the wiring on the suspension, with the other read elementleft unconnected. Thus, when the carrier of FIG. 6 is used as the topcarrier, terminal pads 170, 171 are electrically connected to theappropriate two electrical leads from the cable on the top suspension(e.g., suspension 15 in FIG. 1), and terminal leads 174, 175 connectedto the third transducer 134 are left unconnected. Thus, read element 134is not used. Similarly, when the same carrier of FIG. 6 is used as thebottom carrier, terminals 174, 175 are electrically connected to the twoleads from the cable on the bottom suspension (e.g., suspension 19 inFIG. 1).

Referring now to FIG. 7, there is illustrated a third embodiment of thepresent invention. In the embodiment of FIG. 7, there is a single commoncarrier with a trailing end 300 having an identical pattern ofcomponents that includes the three transducers, five terminal pads180-184, and all of the electrical connectors interconnecting theterminal pads with the three transducers. The embodiment of FIG. 7 issimilar to that of FIG. 6 with the exception that there are only threeterminal pads for the read elements, with one of the terminal pads(i.e., pad 181) being a common terminal pad that is electricallyconnected to both the second read element 132 and the third read element134. During assembly of the disk drive, the common carrier, when used asthe top carrier, has terminal pads 180, 181 electrically connected tothe leads on the top suspension. When used as the bottom carrier, thecommon carrier has terminal leads 181, 182 electrically connected to theleads on the bottom suspension. Thus, in the manner similar to that ofFIG. 6, only one carrier common to both top and bottom sides of the diskneed be manufactured. The uniqueness of the top and bottom carriers isobtained by the wiring connection of the terminal pads to the leads onthe suspensions.

In the preferred embodiments illustrated and described, the common headcarrier is a three-element read/write/read structure. However, it iswithin the scope of the present invention that the three-elementstructure can be a write/read/write structure wherein the centertransducer is a read element and the second and third transducersequally spaced from the center of the read transducer are inductive coilwrite elements.

Also, in the preferred embodiments, the second and third transducers aregenerally equally spaced from the center transducer. This is for diskdrives designed to operate in cylinder mode. However, even in suchdrives, the second and third transducers cannot be exactly equallyspaced from the center transducer because of manufacturing tolerances.For example, if the nominal spacing is in the range of 10 to 100microns, there can be differences in spacing of approximately 0.25 to 1micron due to lithographic alignment tolerances. For disk drivesdesigned to operate in noncylinder mode, the separation distances of thesecond and third transducers from the center transducer can be differentsince there is no requirement that the top and bottom heads be alignedwith one another. In noncylinder mode disk drives, the criteria for thetransducer spacings becomes one of transducer placement. For example, itcan be advantageous for write transducers to always be on the OD side ofthe read transducer for heads on both the top and bottom disk surfacesif a "load/unload" ramp is positioned at the OD of the disk edgebecause, as the head comes off the load/unload ramp, data can beaccessed or read at the same time for either a top or bottom disksurface. This application would require two separate part designs forthe top and bottom transducers unless the three-element design(read-write-read) is used. Thus, a transducer design that allows for thewrite element to lead the read element relative to a disk diameter (ODor ID) for both disk surfaces is advantageous. The three-element designis a single head structure that satisfies this requirement. Anoncylinder mode embodiment can be understood by considering FIG. 3 asrepresenting a noncylinder mode disk drive with the spacing betweentransducer 134 and center transducer 130 being smaller than the spacingbetween transducer 132 and center transducer 130, and with transducer134 of top carrier 110 being electrically connected to pads 140, 141.

The common carrier with the three-element read/write/read head asdescribed above provides the advantage that the manufacturing yield ofthe heads is substantially improved. For example, a process which has anormal yield of 70% for a single read element design could improve to ayield of 95% for a read-write-read design because of the redundancycreated by the extra read element. This is because both read transducerscan be tested before assembly into the disk drive to determine if eitheris bad. If one of the read transducers is bad, and the remaining readelement is good, then the carrier is flagged as being either a top orbottom carrier, depending on whether the good read transducer is thesecond or the third transducer. This is a significant improvement overprior art conventional dual-element heads and side-by-side, dual-elementheads, both of which use two unique and separate carriers, each of whichhas only a single read transducer formed on it. In these prior artheads, if the read transducer is bad after fabrication, the entirecarrier is rejected.

While the preferred embodiments of the present invention have beenillustrated in detail, it should be apparent that modifications andimprovements may be made to the invention without departing from thespirit and scope of the invention as described in the following claims.

What is claimed is:
 1. A magnetic recording disk drive of the typehaving a disk with top and bottom data surfaces, and top and bottomtransducer carriers maintained near their associated disk data surfacesfor reading and writing on the data surfaces, the disk drivecomprising:a control unit for managing reading and writing of data; atleast one data disk having top and bottom data surfaces; a motorconnected to the disk for rotating the disk; an actuator connected tothe top and bottom carriers for simultaneously moving the top carrieracross the top surface of the disk and the bottom carrier across thebottom surface of the disk so the transducers may access data on theirassociated data surfaces; a read/write channel for communicating databetween the control unit and the data surfaces; a top carrier maintainednear the top surface of the disk for supporting read and writetransducers, the top carrier having a back side, a disk side, and atrailing end, the trailing end having an edge near the disk side and anopposite edge near the back side, the trailing end of the top carrierhaving formed on it a pattern of components comprising (a) a firsttransducer having a sensing end oriented toward the disk side edge; (b)second and third transducers generally equally spaced on opposite sidesof the first transducer and having sensing ends oriented toward the diskside edge; (c) five terminal pads near the back side edge for electricalconnection to the transducers, a fourth one of said five pads being acommon pad for electrical connection to both the second and thirdtransducers; and (d) electrical conductors interconnecting the firsttransducer with the first and second terminal pads, the common and fifthterminal pads with the second transducer, and the common and thirdterminal pads with the third transducer; a bottom carrier maintainednear the bottom surface of the disk for supporting read and writetransducers, the bottom carrier having a back side, a disk side, and atrailing end, the trailing end having an edge near the disk side and anopposite edge near the back side, the trailing end of the bottom carrierhaving formed on it a pattern of components identical to the pattern ofcomponents formed on the trailing end of the top carrier; and whereinthe common and third terminal pads of the top carrier are electricallyconnected to the read/write channel and the common and fifth terminalpads of the bottom carrier are electrically connected to the read/writechannel, whereby the second transducer on the top carrier and the thirdtransducer on the bottom carrier are active transducers.
 2. The diskdrive according to claim 1 wherein the first transducer is an inductivewrite transducer, and the second and third transducers aremagnetoresistive read transducers.